JPS63181578A - Video storage device - Google Patents

Abstract

PURPOSE:To eliminate the wasteful use of a storing element by generating a video storage start signal to the storing element for storing a video only under a state in which the output of an A/D converter indicates a predetermined video level. CONSTITUTION:When a switch 2 is turned on after a camera 1 is completely stabilized, if these are synchronizing part and a video part in a video signal, at least more than one of the respective bit output terminals of the A/D converter 6 is changed. This is detected in a microcomputer 11 and held for a fixed time. Under this state, when a vertical synchronizing signal from a synchronizing circuit 8 and a signal indicating that the switch is turned on are inputted, the storage start signal from the microcomputer 11 is applied to the storing element 7 according to the AND thereof and the video can be stored in the storing element 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video storage device for storing video signals.

BACKGROUND ART In recent years, with the decline in the cost of memory elements such as DRAM and SRAM and the spread of digital technology, it has become possible to store video signals such as television signals and camera signals, hold them for a certain period of time, and retrieve them at any time. is being actively carried out.

For example, a television camera is placed at the entrance, and a video signal from the television camera is transmitted indoors to a storage device such as a DRAM or the like in one field of the video signal in an entrance television phone device in conjunction with the operation of a call button located at the entrance. The information is recorded sequentially and used to confirm the presence of guests when the customer is absent.

Hereinafter, with reference to the drawings, a method of storing data in the memory element of the conventional video storage device as described above will be explained.

FIG. 2 shows a conventional video storage device.

In Fig. 2, 1 is a camera that projects an image and outputs a video signal, 2 is a switch for storing the video signal of camera 1, 3 is a video signal buffer circuit that receives the video signal of camera 1, and 4 is a video signal 6 is a pedestal clamp circuit that fixes the pedestal level of the video signal to a constant potential;
6 is an A/D converter that converts the video part of the pedestal flagged video signal from analog to digital; 7 is a storage element such as DRAM that stores the video signal; and 8 is synchronized with the output of the video signal buffer circuit 3. A synchronization signal generation circuit extracts a signal and generates a horizontal synchronization signal, a vertical synchronization signal, and a clock signal phase-synchronized with the synchronization signal; 9 is a counter circuit that counts the signals of the synchronization signal generation circuit 8; 10 is a counter circuit Memory element 7 according to the count value of 9
11 is a microcomputer that controls each circuit. Also, Al
d camera block, B is an image storage block.

The operation of the video storage device configured as described above will be described below.

When camera 1 of camera block A is in an operating state, a video signal is input from camera 1 to video signal buffer circuit 3,
It is output to the filter circuit 4 and the synchronization signal generation circuit 8. After adjusting the frequency characteristics of the video signal in the filter circuit 4,
The frequency band is limited and sent to the pedestal clamp circuit 6. The pedestal clamp circuit 5 processes the video signal so that the pedestal part of the synchronization signal of the video signal is fixed at a constant potential, and as a result, the video part of the video signal to the A/D converter 6 is within a constant potential. It can be paid to. A
The /D converter 6 converts the video portion of the video signal from analog to digital, and inputs the data to the storage element 7. On the other hand, the synchronization signal generation circuit 8 separates the synchronization signal from the video signal, outputs new horizontal synchronization signals and vertical synchronization signals in synchronization with the synchronization signal, and also generates a clock signal.

These signals serve as a sampling clock for the A/D converter 6, a color input for the counter circuit 9, and a control signal for the microcomputer 11.

The horizontal synchronization signal and vertical synchronization signal to the counter circuit 9 are used as reset signals within the counter circuit 9, and the address of the storage element 7 is set in the address setting circuit 1o according to the count value of the clock signal of the counter circuit 9. Set.

Now, when camera 1 of camera block A is in operation and switch 2 is turned on, an ON signal is given to microcomputer 11 of video storage block B, and a synchronization signal and a clock signal are input from synchronization signal generation circuit 8. There is. As a result, the microcomputer 11 outputs a video storage start signal (so-called write signal) to the storage element 7, and the digital data of the video signal from the A/D converter 6 is transferred to the storage element 7 according to the address of the address setting circuit 10.
Then, it functions to cause the memory element 7 to memorize the condyle for a certain period of time (for example, one field of video signal).

Problems to be Solved by the Invention However, in the above-mentioned device, only the synchronous component of the video signal from the camera 1 and the ON state of the switch 2 are detected. Even if the video signal from camera 1 is only the synchronization signal part and there is no video part, such as when it is blocked or immediately after camera 1 is turned on, the video storage operation is performed and the video is stored. Sometimes the original purpose could not be achieved.

The above-mentioned problems are common, and include, for example, delays in the shutter circuit for protecting the internal elements of the camera, and time delays due to aging of the internal elements of the camera.

In view of the above-mentioned problems, the present invention provides a video storage device that can prevent video storage when there is no video portion of a video signal.

Means for solving the problem includes a pedestal clamp circuit, an A/D converter for A/D converting the video portion of the video signal, and a storage element for storing the output of the A/D converter, The video storage start signal to the storage element for storage is generated only when the output of the A/D converter shows a value higher than a predetermined level.

Function: With this configuration, the video signal to be A/D converted is limited to only the video portion because the pedestal level potential is fixed by the pedestal clamp circuit. Therefore, when the video signal is only a synchronization signal, the output of the A/D converter is the same as when there is no video signal itself, and changes only when the video portion of the video signal is present. As a result, if at least one of the output terminals of the A/D converter is detected by the microcomputer and the level is higher than the predetermined pedestal level, the microcomputer maintains that state for a certain period of time. , performs a logical product with another pre-held condition for video storage (for example, after a predetermined period of time has elapsed for the suppression wave of switch 2), and as a result, sends a video storage start signal to the storage element. By outputting, the storage element stores video only when there is a video portion of the video signal.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a video storage device in one embodiment of the present invention. In Figure 1, 1 is a camera, 2 is a switch, 3 is a video signal packer circuit, 4 is a filter circuit,
6 is a pedestal clamp circuit, 6 is an A/D converter, 7 is a storage element, 8 is a synchronization signal generation circuit, 9 is a counter circuit,
10 is an address setting circuit, and 11 is a microcomputer. Further, A is a camera block, and B is a video storage block. The above configuration is the same as the configuration shown in FIG. 2, and the difference from the configuration shown in FIG. 2 is that a part of the output of the A/D converter 6 is applied to the microcomputer 11.

The operation of the video storage device configured as described above will be described below. First, when the camera 1 of the camera block A is in an inactive state, the video signal is not given to the video signal buffer 1 circuit 3, so the synchronization signal generation circuit 8
without outputting a control signal to the microcomputer 11 from
Even if the switch 2 is pressed, the microcomputer does not supply the video storage start signal to the storage element 7, and the storage element 7 does not perform the storage operation. At some times, the video signal includes only a synchronization signal portion and no video portion. In this case, the microcomputer 11 is supplied with a control signal from the synchronization signal generation circuit 8 as a result of the video signal from the camera 1 being supplied to the synchronization signal generation circuit 8 . At this time,
When the switch 2 is turned on, this information is also given to the microcomputer 11, but the output of the A/D converter 6 does not change because there is no video part of the video signal, and the output of the A/D converter 6 does not change. By calculating the logical product of the output of the synchronization signal generating circuit 8 and the operation of the switch 2, the video storage start signal is not applied to the storage element 7.

Then, after camera 1 is sufficiently stable, turn on switch 2.
When the video signal has both a synchronization part and a video part, at least one of the pit output terminals of the A/D converter changes, and this is detected by the microcomputer 11.
If there is an input of the synchronization signal and a signal indicating that the switch 2 is in the ON state at a certain time, the micro combinator 11 gives a storage start signal to the storage element 7 by ANDing them, and the storage element 7 The image can be stored in the memory.

Effects of the Invention As described above, the video storage device of the present invention includes a pedestal clamp circuit that fixes the pedestal level of a video signal to a constant potential, and an A/D converter that A/D converts the video portion of the output video signal of the pedestal clamp circuit. a D converter, and a storage element that stores the output of the A/D converter in response to a video storage start signal, and the video storage start signal to the storage element that stores the video indicates that the output of the A/D converter is in advance. Since the signal is configured to be generated only in a state showing a predetermined video level, it is possible to prevent the video signal from being stored in the storage element when there is no video portion of the video signal.
The memory element is not wasted and the practical effect is great.

FIG. 1 is a block diagram of a video storage device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional video storage device.

A...Camera block, B...Video storage block, 1...Camera, 2...Switch, 3...Video signal buffer circuit , 4...
...Filter circuit, 5...Pedestal clamp circuit, 6...A/D converter, 7...
Memory element, 8...Synchronization circuit, 9...Counter circuit, 10...Address setting circuit, 11
・・・・・・Microcomputer.

Claims (1)

[Claims] A pedestal clamp circuit that fixes the pedestal level of the video signal to a constant potential, an A/D converter that A/D converts the video portion of the output video signal of the pedestal clamp circuit, and a video storage start signal that converts the A/D conversion. and a memory element for storing the output of the A/D converter, and a condition for generating the video storage start signal is that the output of the A/D converter indicates a predetermined video signal level. Video storage device.